"Finance," sighed Mailchimp co-founder and CEO Ben Chestnut Friday at the Inc. Founders House in Austin. "I used to call it 'doing Quickbooks.' Now it's finance."

Chestnut was, in his inimitable way, reflecting on the long, improbable journey that has made his email marketing business what it is today: a company started more or less by accident that notched $600 million in revenue last year, has hundreds of employees and millions of customers, and adds something like 14,000 new customers each day. (It was named Inc.'s Company of the Year in 2017.) 

It was not always this way. In the early days, he recalled, he'd eagerly relate company news to his wife when she got off her shift as a nurse: "I'd say, 'We got two new customers today! Two!'"

While onstage at the Founders House--the inaugural event of the Founders Project, an initiative pairing prominent mentors with early-stage entrepreneurs--Chestnut said the word "customers" a lot. He clearly believes in taking cues from them, which makes sense, because it's how Mailchimp got started. The company grew out of Rocket Science Group, a web-design firm launched just as the tech bubble of the early '00s imploded. At that time, Chestnut said, his business customers all began asking for help with email marketing.

"So I built a little tool for it," he said. The goal was nothing more ambitious than to "make enough revenue to pay for our lunch every day."

He also related the origin story of the now-famous name. Originally it was Chimpmail, but that domain name was taken, so he transposed the words. Monkeys were "a thing" on the web at that time--in the way cats are today--and his parents had had "a pet monkey in Thailand. And they always warned me never to have a pet monkey. So I had this mischievous monkey in my brain."

It took off, to borrow the phrase, gradually and then very suddenly. Chestnut and his co-founder, Dan Kurzius, didn't realize just how much, though, until they held a town hall for all employees. The two were accustomed to doing meetings for 30 or 40 employees. Then "we walked in and there were 200. We acted like the cutups, and the old crew was cheering us on." The newer hands, though, had a vastly different reaction.

The founders were asked about long-term plans for the company, Chestnut said, and he and Kurzius would shoot back, "'We don't need no stinkin' plans!' So they'd ask, 'No, really, why are you being so secretive?' And we'd say, 'There really isn't a plan.'"

"I had people brave enough to tell me, 'That stunk. You can do better.'" Still, he admitted, it took him more than a year to transition from being what he called "the head of all the pirates" to being a more seasoned leader.

Chestnut also revealed that, during the company's recent wholesale rebranding, he raised the idea of changing the company name to Chimp. (Mailchimp, after all, now offers a far broader suite of services than just email marketing.) Research with thousands of customers, though, revealed that the original name still resonated. Their reaction, he said: "I don't know what [Mailchimp] does but I trust it. It sounds quirky--like it gets small business."

"I said, 'That's really interesting,' Chestnut concluded. "Let's not ruin that.'"

The last question for Chestnut, posed by Eric Schurenberg, CEO of Inc.'s parent company Mansueto Ventures: Why did Mailchimp make it when the vast majority of startups don't?

Every entrepreneur, Chestnut replied, eventually faces a "real test. You're going to hit the storm of a lifetime." At that point, it comes down to perseverance. "You don't have be smarter than everyone else. Or all that much better," he said. "You just have to hold on tighter. That's what I'm good at." As ever, Chestnut is understating his skills while getting at a deeper truth.